1. Field of the Invention
The present invention relates to a method of and an apparatus for automatically manufacturing a roof unit for an automobile.
2. Prior Art
Roof units of automotive bodies comprise a roof panel, stiffeners, and other components. In various processes such as sealing, hemming, and welding processes to manufacture roof units, these components are delivered into working stations, positioned in the working stations, and delivered out of the working stations by the operators.
Since, however, there are a considerably large number of components per roof unit, it is not economical to allocate the operators to the respective components. In the sealing process, the roof panel is inverted or turned upside down, resulting in a complex manufacturing procedure.
In each of the processes, a dedicated jig is employed for fixing each component. If a wide variety of roof units are manufactured each in a small quantity, the number of such dedicated jigs used is so large that the cost of manufacture of roof units is high, the time required to replace the jigs is long, and a large space is needed to store the jigs.
Handling of workpieces such as roof panels, e.g., storage of such workpieces, poses a problem because they are relatively large in size and number. It has been attempted to place stacks of workpieces on a carriage. However, it is difficult to stack workpieces while they are being accurately positioned. The shapes of certain workpieces involved make it practically impossible to position the workpieces with accuracy. It is customary for the operator to take out the workpieces manually from the carriage. Such a manual unloading process presents an obstacle to automatization and efficient operation of the entire manufacturing system.
Positioning relatively large workpieces such as stiffeners requires jigs which are larger than the workpieces to be positioned. Replacement of the jigs is therefore cumbersome each time the shape of the workpieces is changed. The more shapes of workpieces, the greater the number of jigs needed, resulting in a greater storage space for the large jigs. In addition, the equipment used to replace the jigs is also large in size.